Probing the paramyxovirus fusion (f) protein-refolding event from pre- to postfusion by oxidative footprinting

Poor, T. A.
Jones, L. M.
Sood, A.
Leser, G. P.
Plasencia, M. D.
Rempel, D. L.
Jardetzky, T. S.
Woods, R. J.
Gross, M. L.
Lamb, R. A.
Poor, T. A. Jones, L. M.; Sood, A.; Leser, G. P.; Plasencia, M. D.; Rempel, D. L.; Jardetzky, T. S.; Woods, R. J.; Gross, M. L.; Lamb, R. A. (2014). Probing the paramyxovirus fusion (f) protein-refolding event from pre- to postfusion by oxidative footprinting. Proceedings of the National Academy of Sciences 111 (25), E2596-E2605
To infect a cell, the Paramyxoviridae family of enveloped viruses relies on the coordinated action of a receptor-binding protein (variably HN, H, or G) and a more conserved metastable fusion protein (F) to effect membrane fusion and allow genomic transfer. Upon receptor binding, HN (H or G) triggers F to undergo an extensive refolding event to form a stable postfusion state. Little is known about the intermediate states of the F refolding process. Here, a soluble form of parainfluenza virus 5 F was triggered to refold using temperature and was footprinted along the refolding pathway using fast photochemical oxidation of proteins (FPOP). Localization of the oxidative label to solvent-exposed side chains was determined by high-resolution MS/MS. Globally, metastable prefusion F is oxidized more extensively than postfusion F, indicating that the prefusion state is more exposed to solvent and is more flexible. Among the first peptides to be oxidatively labeled after temperature-induced triggering is the hydrophobic fusion peptide. A comparison of peptide oxidation levels with the values of solvent-accessible surface area calculated from molecular dynamics simulations of available structural data reveals regions of the F protein that lie at the heart of its prefusion metastability. The strong correlation between the regions of F that experience greater-than-expected oxidative labeling and epitopes for neutralizing antibodies suggests that FPOP has a role in guiding the development of targeted therapeutics. Analysis of the residue levels of labeled F intermediates provides detailed insights into the mechanics of this critical refolding event.
Proceedings of the National Academy of Sciences
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Attribution-NonCommercial-NoDerivs 3.0 Ireland